The present invention relates to a copolymer composition which employs a class of novel siloxane monomers containing both an aromatic ring and vinyl functionality, as a monomer for preparing copolymers in combination with p-(2-hydroxy hexafluoroisopropyl)styrene (HFIS). Copolymers comprising variable amounts of the monomers are transparent to visible light, have a high refractive index, and are useful, inter alia in fabricating lenses, especially contact lenses and intracameral devices such as corneal inserts and intraocular implants. Contact lenses comprise generally fillerless, oxygen transportable hydrolytically stable, biologically inert, transparent plastic bodies which are prepared from polymerization, or copolymerization of monomers. The novel class of siloxane monomers containing both an aromatic ring and vinyl functionality are the subject of our copending commonly assigned application, Ser. No. 801,259, filed Nov. 25, 1985, now U.S. Pat. No. 4,633,003 Park and Falcetta, and entitled NEW SILOXANE MONOMERS FOR OPHTHALMIC APPLICATIONS. The copolymers of this invention which contain this monomer are optically clear and colorless.
The polymers and copolymers described herein can be usefully employed for making "hard" or "soft" contact lenses, intraocular implants, intracorneal implants, semisoft contact lenses, as well as in other biomedical applications. Importantly, the copolymers of this invention, that is the combination of the novel class of siloxane monomers of Ser. No. 801,259 and HFIS, are especially adapted for, and suitable in, making hard gas permeable contact lenses, with the HFIS contributing to wettability without any negative impact on oxygen permeability. In fact, oxygen permeability is enhanced. The copolymers may also have other uses such as permeable films, etc., but the primary description given will emphasize lens utility.
Hard contact lenses have the advantages of excellent machinability, excellent stability, and excellent visual clarity. However, hard contact lenses have their disadvantages, as well. Generally for many, including the most common hard lenses, i.e. those made of polymethyl methacrylate (PMMA), oxygen permeability is low and the hydrophilic properties are poor.
It is important and essential that the cornea have access to atmospheric oxygen in order that an oxygen-carbon dioxide exchange can occur. Put another way, without constant eye exposure to the atmosphere, a state of oxygen edema can occur within the eye, which is potentially capable of causing damage. Thus, hard contact lenses, while having many practical advantages, generally are not altogether satisfactory because they most often have poor oxygen permeability.
A good hard contact lens would have not only excellent oxygen permeability, but also excellent tear-fluid wettability. Wettability is important in that if the lens is not wettable it cannot be comfortably worn in the eye. The patient will perceive the lens as uncomfortable and scratchy, absent good wettability.
Generally, in the past, polymer formulation for optical lens products has involved an initial determination as to whether one was formulating either a hard lens or a soft lens, followed by formula manipulation within a distinctly different class of monomers useful for one type, but not necessarily useful for the other. As explained in our co-pending earlier referenced application Ser. No. 801,259, it has now been found possible to make contact lenses, involving as a siloxane monomer ingredient of variable presence, a monomer which can be adapted for making either hard or soft lenses. In this present invention, the novel class of siloxane monomers is combined with a comonomer of preferred HFIS or other hydroxyfluoroalkylstyrene, which contributes both wettability and oxygen permeability.
Indeed, it is an object of the present invention to provide in combination with our earlier described class of novel siloxane monomers which have both an aromatic ring functionality and vinyl functionality at certain stereo-directing positions, a hydroxyfluoroalkylstyrene such as p-(2-hydroxy hexafluoroisopropyl)styrene (HFIS), resulting in copolymers useful as materials for making a wide variety of types of optical products, especially gas permeable contact lenses and ocular implants.
A further object of the invention is to provide a copolymer combination of the type specifically mentioned above which is not only of good oxygen permeability, but which is highly compatible with other monomers, and which, when copolymerized with other minor monomers provides wettability, without sacrificing oxygen permeability.
A still further object of the present invention is to provide hard gas permeable contact lenses which contain as a main ingredient of variable presence, the hereinafter defined combination of monomers of the present invention.
A still further object of the present invention is to provide hydroxyfluoroalkylstyrenes such as the preferred HFIS as a monomer for use in biomedical lens devices to improve wettability, without any significant impact on oxygen permeability.
A further object of the present invention is to provide a copolymerizable compound suited for preparing contact lenses which have good oxygen permeability, are machineable, and which can be used with or without other minor monomer modifiers for hard gas permeable contact lenses which can be comfortably worn.
A still further object of the present invention is to prepare a copolymer combination which can be copolymerized with or without other minor, modifying monomers to provide a copolymer useful for optical products, particularly gas permeable hard contact lenses, wherein the copolymer has a DK, i.e. oxygen permeability constant value within the range of from about 12 to about 70, and which also has a highly wettable surface. Such lenses are comfortable, when worn show no evidence of substantial corneal edema, are of good machineability, are dimensionally stable, are tear wettable, and as well have sufficient lipophilicity to optimally interact with tear fluid.
The method and means of accomplishing each of the above objectives, as well as others will become apparent from the detailed description of the invention which will follow hereinafter.